Since the announcement of a thaw with the United States, Cuba seems suspended between potentially very different histories: what was, what is and what’s to be. Of the three, the knowable one is, of course, the past, and a substantial and dramatic part of the record is in the form of photographs. The International Center of Photography has a collection deep enough to tell that visual story, and is doing so, with some outside additions, in “¡Cuba, Cuba! 65 Years of Photography” at the Southampton (N.Y.) Art Center through Sept. 7.